1. Field of the Invention
This invention relates in general to automated food vending machines of the type having a plurality of dispensing trays or shelves which may be moved outwardly from the machine housing to facilitate loading the shelves with the various food products to be dispensed. More particularly, this invention relates to an interlock system between the door of the vending machine and the shelves. This interlock system prevents the shelves from being pulled outwardly until the door is fully open and also prevents the door from being closed when any of the shelves are pulled out of the housing.
2. Description of the Prior Art
Automated vending machines are well known for dispensing food products upon insertion by a purchaser of a required amount of money. Such vending machines have various kinds of dispensing mechanisms depending upon the particular types of food products which are being vended. One well known class of such vending machines is that known in the trade as helical coil vending machines or, alternatively, as spiral vendors. U.S. Pat. No. 4,061,245, issued on Dec. 6, 1977 to Joseph A. Lotspeich and assigned to the assignee of the present invention, is a typical example of such a helical coil vending machine. Such machines are widely used for dispensing pre-packaged food products including rolled candy, mints and the like, and for dispensing so called "snack" products, such as packages containing potato chips, pastries and the like.
Most helical coil dispensing machines customarily include a housing which supports a plurality of vertically spaced shelves. Each of the shelves usually includes a plurality of elongated dispensing coils which run from front to back on the shelf. The rear end of each dispensing coil is operatively connected to an electric motor for selectively rotating the coil. Such rotation advances the food products received between the convolutions of the coil in a step by step manner along the surface of the shelf. Upon each consecutive rotation of the coil, the product held in the foremost convolution is dispensed over the end of the shelf into a discharge space. The product carrying shelves in most of the vending machines of this type may be slid out of the machine when a door is opened to allow a serviceman to easily fill the coils with the food products to be dispensed. If the shelves could not be pulled out of the machine, the task of loading the coils would be difficult due to the lack of clearance space between adjacent shelves and the consequent difficulty in reaching the rearmost convolutions of the coil.
Vending machines which utilize movable shelves are sometimes damaged by careless or inexperienced servicemen. For example, servicemen sometimes fail to properly return all of the shelves in the vending machine to their fully retracted position inside the vending machine housing before attempting to close the door of the machine. Thus, the door will strike any of the shelves which are protruding outwardly from the machine as the serviceman attempts to close it. This contact often damages either the shelf and the dispensing coils contained thereon or, in some instances, the door. This requires that the vending machine be repaired. The need for such repair is disadvantageous and costly. In addition, the same damage can also occur when the serviceman attempts to pull a shelf out of the housing before the door is fully open.
Various devices have been proposed to prevent any shelves from being pulled out until the vending machine door is fully open and, thereafter, to prevent the door from closing when all of the shelves have not been returned to their fully retracted position. U.S. Pat. No. 4,046,440 discloses a device of this type. In this device, a locking bar is operatively connected to the pivot structure of the vending machine door. The locking bar activates a plurality of swingable latches which may be engaged with a locking lug on each of the shelves. Each of the shelves also includes a horizontally extending abutment on the side thereof. If each of the shelves is not in a fully retracted position when the operator attempts to close the door, the latches on the locking bar will engage the abutment. This prevents the locking bar from being moved to a position at which it will allow the door to be closed. The door can be closed only when all the latches do not engage any portion of the abutments on the dispensing shelves. In addition, none of the shelves can be pulled out of the machine until the locking bar drops down to clear all the latches with the locking lugs on the shelves. The downward movement of the locking bar occurs only when the door is fully open.
A disadvantage with the device noted above is the coaction which is required between the abutments and the latches. In other words, the above-noted device requires the presence of something on a shelf (i.e., the abutment) to prevent the door member from being closed. It is possible that not all vending machine shelves will be provided with such abutments or, if they are so provided, the abutments might not be of uniform length in different machines. Such machines would have to be modified to accept the above-noted device. In addition, the abutment provided on the shelves does not usually run the full length of the shelf. Thus, in certain cases, the door can be closed even when the shelves are extending outside of the housing where the shelf is pulled out sufficiently far such that the abutment has cleared the latch (e.g., the latch is in front or back of the abutment).